4 Replies Latest reply on Aug 2, 2013 10:24 AM by Krishh M

    Static Vs Nonlinear

    Krishh M

      Hi,

       

      What is the method to study displacement and streses under compressive pressure on Aluminum housing having optical glass port (say. BK7)? Static study or Nonlinear? I am interestested to see both glass and aluminum behaviour under pressure.

       

      thaks,

      mkp

        • Re: Static Vs Nonlinear
          Jared Conway

          you'd move from static to nonlinear if:

          1. you have nonlinear material

          2. you have large displacements and the stiffness of the components change significantly

          3. you need to sequence the analysis conditions or analysis conditions that change over "time"

          4. contact conditions that change location over the analysis

           

          static stress is linear static stress, linear materials, all loads applied at the same time, all loads slowly.

           

          is there something about the aluminum or glass that you think requires nonlinear? or something about your setup?

            • Re: Static Vs Nonlinear
              Krishh M

              Obviously aluminum is ok, but deosn't BK7 behave nonliniar under heavy pressure like 8kpsi? - I m not sure about this. Or it just act as any brittle material but linear? pls. correct me here.

               

              all I want find out is more realistic estimation of displacement of both materials under pressure. So do you think static study give better estimation?

               

              - On same note, how to know a marerial behaves non linear, just by looking at material spec? How about engineering plastics like HDPE,Delrin..etc?

               

              -What if I want to study behaviour of parts in assembly both linear and nonlinear (say Aluminum housing and Oring)? Have to run nonlienar study for whole assembly?

               

              thank you so much.

              mkp.

                • Re: Static Vs Nonlinear
                  Jared Conway

                  in the real world, everythign is nonlinear and transient (time dependent)

                   

                  if you can "afford" to run a nonlinear dynamic, it is likely to be the most accurate. but as engineers, we know that there are always assumptions we can make to bring down the computation cost and still get results that are reasonable.

                   

                  regarding your other questions. how to know if the material is nonlinear > look at the curve, and know where on the curve that the loading will lie. if you go past the straight section > nonlinear. but also consider that displacement creates nonlinearity which is separate from material nonlinearity.

                   

                  with a nonlinear analysis, you can turn on features and turn off features. for example make some parts nonlinear (plastic) and some elastic. you can also turn off large displacement if you want. but in the long run, the nonlinear solver still gets used.

                   

                  if you ahvent' done so already, i'd highly recommend a solidworks simulation and nonlinear class to get more information on this.